The influence of CTAB and gum arabic on the precipitation of α-FeOOH in a highly alkaline medium

• CTAB and GA influenced the precipitation of α-FeOOH in highly alkaline medium.
• The nano/microstructural and phase changes in the precipitates were monitored.
• Surface interactions governed the precipitation phenomena.

The influence of cetyltrimethylammonium bromide (CTAB) and gum arabic (GA) on the precipitation of α-FeOOH in a highly alkaline medium was investigated using XRD, 57Fe Mössbauer, FT-IR and FE-SEM. In absence of CTAB and GA long α-FeOOH rods of nanosize width were obtained. For predetermined concentrations of CTAB added to the precipitation system the formation of a small fraction of α-Fe2O3 was noticed, whereas the length of the α-FeOOH rods significantly decreased and α-FeOOH dendrites were also found. The effect was specifically pronounced when GA was added to the precipitation system. The formation of ferrihydrite-like phase was detected, which suppressed the crystal growth of α-FeOOH on one side and forced the nucleation and growth of α-Fe2O3 on the other. Microstructural changes in the precipitates were also monitored. The phase transformation and changes in the nano/microstructure of the precipitates found can be explained taking into account the surface interactions between CTAB or GA with nuclei and crystallites (particles) during the kinetics investigated.